Rolling element bearings (“rolling bearings”) are well-known to comprise a plurality of rolling elements (balls, rollers, or the like) situated between two rings or races that are annular in configuration. For purposes of strength, economy and durability, bearings are often made from metal, e.g., steel.
Airborne systems commonly make use of large azimuth rolling bearings, e.g., bearings having an inner diameter of about 15.25 centimeters (cm) (6 inches (in.)) or more. The bearings are installed in rotating mechanisms (each of which comprises a rotating structure that rotates relative to a support structure) that have to be made from light aluminum alloys in order to control weight. Such bearings and rotating mechanisms can be found in airborne applications including electro-optical targeting system gimbals for camera mounts, search light gimbals, and elsewhere. Conventional bearings are installed and fitted in such mechanisms for optimum stiffness and rotational torque at ambient temperature, but the bearings exhibit significant variations in performance at extremes of temperature in actual use. At one temperature extreme, the bearing will be internally over-loaded to much higher stiffness and rolling friction torque than is optimal; yet at another extreme, the bearing internal preload may be compromised, resulting in loss of stiffness or excessive deflection. Such temperature-related variations in bearing performance are caused by differences in coefficient of thermal expansion (CTE) between the bearing materials (e.g., hardened steels) and the materials used for the rotating mechanism (e.g., aluminum alloys). These variations in bearing performance have to be carefully analyzed, and their consequences mitigated, often necessitating utilization of larger drive motors and/or using more expensive support structure alloys with CTE properties as close to bearing steel as possible.